The present invention relates to an electromagnetic strut for a vehicle suspension unit.
Japanese Patent Application First (unexamined) Publication No. 2-37016 claiming priority on U.S. Pat. application Ser. No. 200,025 filed May 27, 1988, now U.S. Pat. No. 4,892,328, issued Jan. 9, 1990 to Kurtzman et al., which discloses an electromagnetic strut. This known electromagnetic strut includes a magnetic device surrounded by a coil assembly. The magnetic device includes a rod of a ferromagnetic material and a permanent magnet attached to the rod. The magnetic device is movable relative to the coil assembly in response to movement of a vehicle body relative to a wheel assembly. This known electromagnetic strut has a potential problem that the strength of a magnetic field is difficult to increase to a sufficiently high level. If, for example, it is demanded to increase a maximum stroke, the magnetic path is elongated, resulting in an increased resistance to the magnetic path. If it is required to increase the effective cross sectional area of the magnetic path, the rod with increased diameter is needed, resulting in an increase is radial dimension of the strut.
Accordingly, the present invention aims at solving the potentional problem incorporated in the known electromagnetic struts.
A specific object of the present invention is to provide an electromagnetic strut which is improved such that a magnetic field with a sufficiently great strength is maintained irrespective of a change in the maximum stroke.
Another specific object of the present invention is to provide an electromagnetic strut which is improved such that a magnetic path has a sufficiently large effective cross sectional area without causing any increase in a radial dimension of the strut.